The present invention relates to a photographic camera, and more particularly to a photographic camera with various features such as automatic film winding, zooming and automatic date recording.
In recent years, in photographic cameras, in particular compact cameras, it has become increasingly popular to have various automatic features, such as automatic exposure, automatic focusing, and automatic film winding and rewinding.
An automatic camera equipped with automatic film winding and rewinding features is adapted to place a first frame of a film in an exposure aperture of the camera upon closing a back door after loading the film in the camera. The film is wound up by one frame every exposure and, when all of the possible exposures of the film are made, the film is automatically rewound. This film rewinding is caused when a torque sensor detects a predetermined tension in the film.
To wind up the film by one frame every exposure, the camera is provided with a sprocket wheel in engagement with perforations of the film so as to be rotated by the advance of the film. The sprocket wheel produces pulse signals one for each perforation and, upon having produced a predetermined number of pulse signals, provides a stop signal (S.sub.o) for stopping the motor.
Such an automatic film winding camera has various operation modes and is driven by means of battery power. Upon replacing a battery, the camera operation modes are cleared and reset to an initial operation mode.
An automatic camera equipped with a zoom lens is adapted to change the focal length of the zoom lens by means of a motor. That is, when turning on a long focal length selection switch or a short focal length selection switch, the motor is actuated to shift the zoom lens so as to have a long focal length or a short focal length. Upon turning off the switch to stop the zoom lens at a position wherein it has a desired focal length, an encoder detects the stopped position of the zoom lens to provide a signal indicating the given focal length. The signal is used as one of the data for a proper exposure. The zoom lens is covered and protected with a lens barrier when the camera is not used.
To shift the zoom lens so as to change its focal length, it is customary to use a motor. For light weight, a single motor is incorporated in the camera and used for winding and rewinding the film and shifting the zoom lens. For the same purpose, a battery or batteries are used not only to actuate the motor but also to charge an electronic flash and operate a microcomputer for controlling the camera.
The battery used in such a camera is heavily loaded and soon discharged. This requires the replacement of the battery during camera operation, often causing operation errors. That is, when replacing the battery while the camera is in an electronic flash charging mode, a film winding mode, or a focal length changing mode, the operation mode is cleared. For example, upon replacing the battery while the camera is in the film winding mode, the motor is powered on and the camera will carry out the first frame setting operation because the camera is set in the initial film setting mode due to the replacement of the battery and cannot determine that the film was loaded before the replacement of the battery. In the initial film setting mode, a film leader of the film is wound up by a length substantially equal to that of four frames. Accordingly, if the replacement of the battery takes place after several exposures of the film four frames of the film are wasted.
If a barrier switch is operated so as to close the lens barrier before replacing the battery, the lens barrier will close upon the replacement of battery. When the zoom lens is shifted forward, the lens barrier bumps the zoom lens and will be damaged.